Bäcker, Claus MaximilianHorst, FelixAdi, WihanBäumer, ChristianGerhardt, MarcelJentzen, WalterKazek, Sandra LauraKröninger, KevinSchuy, ChristophVerbeek, NicoWeingarten, JensWulff, JörgTimmermann, Beate2022-03-232022-03-232021-08-02http://hdl.handle.net/2003/40825http://dx.doi.org/10.17877/DE290R-22682The natC(p,x)11C reaction has been discussed in detail in the past [EXFOR database, Otuka et al. (Nuclear Data Sheets 120:272–276, 2014)]. However, measured activation cross sections by independent experiments are up to 15% apart. The aim of this study is to investigate underlying reasons for these observed discrepancies between different experiments and to determine a new consensus reference cross section at 100 MeV. Therefore, the experimental methods described in the two recent publications [Horst et al. (Phys Med Biol https://doi.org/10.1088/1361-6560/ab4511 [Titel anhand dieser DOI in Citavi-Projekt übernehmen] , 2019) and Bäcker et al. (Nuclear Instrum Methods Phys Res B 454:50–55, 2019)] are compared in detail and all experimental parameters are investigated for their impact on the results. For this purpose, a series of new experiments is performed. With the results of the experiments a new reference cross section of (68±3) mb is derived at (97±3) MeV proton energy. This value combined with the reliably measured excitation function could provide accurate cross section values for the energy region of proton therapy. Because of the well-known gamma-ray spectrometer used and the well-defined beam characteristics of the treatment machine at the proton therapy center, the experimental uncertainties on the absolute cross section could be reduced to 3%. Additionally, this setup is compared to the in-beam measurement setup from the second study presented in the literature (Horst et al. 2019). Another independent validation of the measurements is performed with a PET scanner.en530Text